Not Applicable
Not Applicable
Not Applicable
The present invention relates to electric solenoid operated valves and particularly relates to the problem of the noise generated by such solenoids when subjected to operating environment of relatively high vibration such as is encountered in motor vehicle applications. Furthermore in certain solenoid operated valve applications where high pressures are encountered of the order of 350 psi (2415 kPa) a significant force is required on the moveable armature/valve member in order to effect opening of the valve against the pressure forces. The required force on the armature often results in high velocity of the armature during opening; and, impact of the armature against the stop or pole piece adjacent the armature generates a significant amount of noise upon closing of the working air gap.
Heretofore, attempts to reduce the velocity of the armature have been generally directed toward increasing the bias on the armature which in turn results in the requirement for greater force in moving the armature to open the valve. Where a limited amount of power is available for the solenoid, and particularly where increases in the number of ampere turns of the coil would result in prohibitive cost increase for valves produced in high volume mass production, increasing the bias force on the armature has not be an option. This is particularly the case in automotive applications where a solenoid operated valve is employed for controlling the flow of refrigerant between the condenser and the evaporator inlet for the vehicle passenger compartment air conditioning system. In such systems, it is common practice to mount the electrically operated expansion valve on the evaporator housing which is usually attached to the engine firewall. Thus, operating noise generated in the expansion valve is transmitted to the vehicle fire wall structure and has been found to resonate through the vehicle structure and provide objectionable levels of noise in the vehicle cabin.
Solenoid operated valves, when employed in systems subject to sudden pressure changes and changes in phase of fluid flowing through the valve, such as is the case for liquid/vapor refrigerant, are particularly susceptible to noise generated within the solenoid operator by virtue of the armature velocity resulting from the forces required to effect movement of the armature over a wide range of pressures and fluid conditions.
Thus, it has long been desired to provide a solenoid operated valve, particularly one which is suitable for valving liquid/vapor refrigerant in an air conditioning system for motor vehicle usage which is relatively low in manufacturing cost in high volume production and which eliminates the noise generated by rapid armature movement against a stop and which is easy to manufacture and robust in service.
The present invention provides a solution to the above-described problem of finding a way or means of quieting an electrically energized solenoid operated valve in which noise generated by high armature velocities and impact of the armature against a limit stop is minimized or substantially eliminated. The valve of the present invention utilizes a solenoid for operating a pilot valve member for creating a pilot flow resulting in a reduced pressure differential which enables opening a main valve member and is particularly suitable for use as a shutoff valve for high pressure liquid/vapor refrigerant flow in a motor vehicle air conditioning system.
The valve of the present invention utilizes a fluid dashpot disposed internally of the solenoid coil and within a sealed armature guide and provides for viscous dampening of the armature movement when subjected to substantial magnetomotive force on the armature. The dashpot limits the armature velocity thereby controlling the impact of the armature with the pole piece upon closing of the working air gap. The dashpot of the present invention utilizes the fluid medium flowing through the valve as the operating fluid for the dashpot. In the presently preferred practice, the dashpot is connected to a pilot valve member. A minimum of force is required to overcome the return or closing spring provided for the pilot valve member. The solenoid operated valve of the present invention thus employs an internally disposed fluid dampening device in the form of a dashpot to limit the velocity of the armature upon energization of the solenoid and thereby minimizes the noise generated by the armature impacting a limit stop due to the magnetomotive force of the solenoid. The valve construction of the present invention is particularly suitable for pilot operated solenoid valves employed for controlling the shutoff of liquid/vapor fluids as encountered in refrigerant systems and particularly such systems as they are utilized in motor vehicle cabin air conditioning systems.